LMZ31506H_15 Datasheet, PDF (24/35 Pages) Texas Instruments – 6A SIMPLE SWITCHER® Power Module with 4.5V-14.5V Input in QFN Package

LMZ31506H
SNVS996 – JULY 2013
www.ti.com
Programmable Undervoltage Lockout (UVLO)
The LMZ31506H implements internal UVLO circuitry on the VIN pin. The device is disabled when the VIN pin
voltage falls below the internal VIN UVLO threshold. The internal VIN UVLO rising threshold is 4.5 V(max) with a
typical hysteresis of 150 mV.
If an application requires either a higher UVLO threshold on the VIN pin or a higher UVLO threshold for a
combined VIN and PVIN, then the UVLO pin can be configured as shown in Figure 41 or Figure 42. Table 8 lists
standard values for R_UVLO1 and R_UVLO2 to adjust the VIN UVLO voltage up.
R_UVLO1
R_UVLO2
PVIN
VIN
INH/UVLO
R_UVLO1
R_UVLO2
PVIN
VIN
INH/UVLO
Figure 41. Adjustable VIN UVLO
Figure 42. Adjustable VIN and PVIN Undervoltage
Lockout
Table 8. Standard Resistor values for Adjusting VIN UVLO
VIN UVLO (V)
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
R_UVLO1 (kΩ) 68.1
68.1
68.1
68.1
68.1
68.1
68.1
68.1
68.1
68.1
68.1
R_UVLO2 (kΩ) 21.5
18.7
16.9
15.4
14.0
13.0
12.1
11.3
10.5
9.76
9.31
Hysteresis (V) 400
415
430
450
465
480
500
515
530
550
565
For a split rail application, if a secondary UVLO on PVIN is required, VIN must be ≥ 4.5V. Figure 43 shows the
PVIN UVLO configuration. Use Table 9 to select R_UVLO1 and R_UVLO2 for PVIN. If PVIN UVLO is set for less than
3.0 V, a 5.1-V zener diode should be added to clamp the voltage on the UVLO pin below 6 V.
> 4.5 V
R_UVLO1
R_UVLO2
VIN
PVIN
INH/UVLO
Figure 43. Adjustable PVIN Undervoltage Lockout, (VIN ≥4.5 V)
Table 9. Standard Resistor Values for Adjusting PVIN UVLO, (VIN ≥4.5 V)
PVIN UVLO (V)
R_UVLO1 (kΩ)
R_UVLO2 (kΩ)
Hysteresis (V)
2.0
68.1
95.3
300
2.5
68.1
60.4
315
3.0
68.1
44.2
335
3.5
68.1
34.8
350
4.0
68.1
28.7
365
4.5
68.1
24.3
For higher PVIN UVLO voltages see
Table UV for resistor values
385
24
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